It's all a matter of linguistics. Even though it's basically the same device, calling it a "Parking Guage" disassociates it with the types who scraped curbs using curb feelers on their second hand Cadillacs in urban centers
That Ms Joan Crawford was a real nice purdy lady. But wheoooooo when I ask her to look in dat trunk. She got all kinda ugly.
I wonder as to how many serious accidents had to take place, before they got it into their thick noggins that bare concrete slabs on freeways weren't the best of ideas